1. Field of the Invention
This invention relates generally to fluid pressure operated tools and more particularly to an improved fluid pressure operated percussion tool and nail driver.
2. Prior Art
As will appear from the later description, certain features of the invention may be utilized in a wide variety of fluid pressure operated percussion tools. These features, however, are particularly useful in, and another feature of the invention is limited in usefulness to, nail drivers. For this reason, the invention will be described in the context of a nail driver.
The prior art is replete with a vast assortment of fluid pressure operated nail driving tools. While these nail driving tools may differ substantially in their structural details, most if not all are characterized by a body containing a cylinder and a power piston movable in the cylinder and having a plunger-like hammer or driver extending axially through the front end of the cylinder into an external guideway on the body. Trigger actuated valve means are provided for admitting a working fluid, such as air, into and venting the fluid from the opposite or rear cylinder end in such a way as to effect driving of the power piston through a forward working stroke and a following rearward return stroke in its cylinder. This motion of the piston, in turn, drives the nail driver through a nail driving stroke and a following return stroke in its guideway.
Mounted removably on the tool body adjacent the nail driver guideway is a nail magazine including a spring loaded follower or other means for feeding nails in succession into the guideway in front of the nail driver. During each driving stroke of the nail driver, the latter strikes the head of the nail currently positioned in the guideway and drives the nail forwardly through the open end of the guideway into a workpiece. The driver is then returned rearwardly to its initial retracted position. During this return stroke of the driver, when its front tip finally clears the nail infeed opening, another nail is fed into the guideway in readiness to be driven into a workpiece during the next driving stroke of the driver.
A variety of valving arrangements have been devised for pressurizing and venting the tool power cylinder to effect the tool operating or nail driving cycle described above. This invention is concerned with valving arrangements of the class which utilize a trigger operated pilot valve means for actuating a main fluid pressure operated cylinder valve that controls actual pressurizing and venting of the power cylinder. Nail driving tools having valving arrangements of this class are described in U.S. Pat. Nos. 3,194,324; 3,253,760; and 3,820,705. Other nail driving tools are described in U.S. Pat. Nos. 2,872,901; 3,081,740; 3,081,741; 3,081,742; 3,084,672; 3,086,207; 3,094,900; 3,106,136; 3,229,589; 3,622,062 and 3,596,821. While these patented valving arrangements and nail driving tools are perhaps capable of nail driving operation, they are relatively complex in construction, costly to fabricate, embody a relatively large number of parts and hence are prone to mal-function and costly and time consuming to repair, and are otherwise not totally satisfactory.
Another problem area of the existing nail driving tools resides in their nail magazines. In the past, these magazines have been attached to the tool body in a manner such that the repeated impact forces generated during tool operation often caused bending, cracking and other damage of the magazines. Such damage, of course, incapacitates the entire tool and is often difficult and time consuming to repair.